Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932397Ab2HFSWd (ORCPT ); Mon, 6 Aug 2012 14:22:33 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:56231 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932347Ab2HFSWc (ORCPT ); Mon, 6 Aug 2012 14:22:32 -0400 Message-ID: <50200AEF.5080904@us.ibm.com> Date: Mon, 06 Aug 2012 11:20:31 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0 MIME-Version: 1.0 To: Sasha Levin CC: Avi Kivity , paulmck@linux.vnet.ibm.com, "linux-kernel@vger.kernel.org" , mingo@kernel.org, a.p.zijlstra@chello.nl, prarit@redhat.com, tglx@linutronix.de Subject: Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6 References: <500ED719.2010002@gmail.com> <50112D3B.4020201@redhat.com> <50127B16.5040401@gmail.com> <50153138.4020304@redhat.com> <5015A5A8.7030601@gmail.com> <50161D5E.4030009@redhat.com> <50165046.9020705@gmail.com> <501654D3.7020504@redhat.com> <50168162.4010508@gmail.com> <50168981.3000001@redhat.com> <501EA58D.4090606@gmail.com> <501FFD2A.4010905@us.ibm.com> In-Reply-To: <501FFD2A.4010905@us.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12080618-5518-0000-0000-000006A040C9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1084 Lines: 26 On 08/06/2012 10:21 AM, John Stultz wrote: > On 08/05/2012 09:55 AM, Sasha Levin wrote: >> On 07/30/2012 03:17 PM, Avi Kivity wrote: >>> Possible causes: >>> - the APIC calibration in the guest failed, so it is programming too >>> low values into the timer >>> - it actually needs 1 us wakeups and then can't keep up (esp. as kvm >>> interrupt injection is slowing it down) >>> >>> You can try to find out by changing >>> arch/x86/kvm/lapic.c:start_lapic_timer() to impose a minimum wakeup of >>> (say) 20 microseconds which will let the guest live long enough for you >>> to ftrace it and see what kind of timers it is programming. >> I've kept trying to narrow it down, and found out It's triggerable >> using adjtimex(). Sorry, one more question: Could you provide details on how is it trigger-able using adjtimex? thanks -john -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/